Improve positions recording for calls.

src/x64/assembler-x64.h

Index: src/x64/assembler-x64.h
diff --git a/src/x64/assembler-x64.h b/src/x64/assembler-x64.h
index bbc101062760f84eac4b1e2d6fa4a08a8dd858ec..c7f763222e6f2f53b7d17149808753b0311565ad 100644
--- a/src/x64/assembler-x64.h
+++ b/src/x64/assembler-x64.h
@@ -1174,13 +1174,9 @@ class Assembler : public Malloced {
   // Use --debug_code to enable.
   void RecordComment(const char* msg);
 
-  void RecordPosition(int pos);
-  void RecordStatementPosition(int pos);
-  bool WriteRecordedPositions();
-
   int pc_offset() const { return static_cast<int>(pc_ - buffer_); }
-  int current_statement_position() const { return current_statement_position_; }
-  int current_position() const { return current_position_; }
+
+  PositionsRecorder* positions_recorder() { return &positions_recorder_; }
 
   // Check if there is less than kGap bytes available in the buffer.
   // If this is the case, we need to grow the buffer before emitting
@@ -1404,11 +1400,8 @@ class Assembler : public Malloced {
   // push-pop elimination
   byte* last_pc_;
 
-  // source position information
-  int current_statement_position_;
-  int current_position_;
-  int written_statement_position_;
-  int written_position_;
+  PositionsRecorder positions_recorder_;
+  friend class PositionsRecorder;
 };